What Steam Game Have You Spent The Most Hours Playing?

The Lord of the Rings Online. Easily 500 hours.

Shogun 2 120+

Borderlands 2

Mount and Blade Warband for 84 hours. Time well spent.

Chivalry: Medieval Warfare 38h

I have not played anything like until this year to be honest.

Team Fortress 2.

I'm sure it is Just cause 2 but most of my playing time was offline so steam didn't recorded it.

Garry's mod

dota 2 about 250 hours :)

XCOM Enemy Unknown

Guild Wars, 306 hours

Team Fortress 2 exactly 777 hours :D

Counter Strike 1.6 - 1469 hrs.

Left 4 Dead 2 - 1600 h

Counter Strike Source

Borderlands 2 - 71.5 hrs on record
Borderlands - 49.3 hrs on record
Torchlight - 20.5 hrs on record

Everything else is under 10 hours. I really need to play other games in my library.

on steam: cs go 130

terraria 43

off steam:

dragon age origins (around 200-250)

oblivion (around 150-200)

The Binding of Isaac

Valve games like L4D2, CS and TF2.

36h is like nothing to some people. :D

Tf2 1630hs

Counter Strike - 1400 hours on Steam + another 1000 hours on Non-Steam version over the last 10 years.

141 in tf2. (not idling)
131 in Black OPs MP.
113 in Skyrim.

Dota 2 140 Hours and counting

I've spent 285 hours on Team Fortress 2.

Hmm, right now it`s Battlefield Bad Company 2 at 56 hours, not that many hours. The 2nd game I ever had on Steam. The 1st was Lost Planet 1, but I got it before they started counting hours played.